curses

curses is terminal-independent screen-painting and keyboard-handling facility for text-based facilities The first curses library was put together at UC Berkeley in 1980 to support the Rogue computer game, using an earlier library called termcap which had been used in the vi editor. This library was almost single-handedly to credit for moving Unix past the line-oriented interfaces inherited from the teletype days. Bell Labs later released enhanced curses libraries in System III and System V, but the source code was not made available, so throughout the 80s software programmers relied on the older BSD curses library. Open-source developers took on the challenge in the early 90s and created ncurses, a Unix library meant to finally recover and overtake the capabilities of the Bell Labs curses library as FOSS.

Command	Effect
stdscr	conventional name for the curses instance, from C
curses.wrapper	function that is passed the name of the main function i.e. wrapper(main), and which manages the details of building up and tearing down the terminal modifications
stdscr.clear()	clear the screen
stdscr.getch()	read a keypress, or -1 if no key has been pressed yet
stdscr.addstr()	similar to "print", text output to screen
curses.flushinp()	clear out anything that the user has typed in
stdscr.nodelay(True)	doesn't wait for input, making getch non-blocking

Simple demo

import curses
stdscr=curses.initscr()
curses.endwin()

Less simple

import curses
stdscr = curses.initscr() # Initialization; window object returned is typically called "stdscr" following the convention in C
curses.noecho() # Turn off displaying keys pressed on-screen, allowing for interactivity
curses.cbreak() # Instantaneous reaction to keypresses, instead of waiting for Enter
stdscr.keypad(True) # special keypresses

# Preparing to close by undoing the changes made to the terminal above
curses.nocbreak()
curses.echo()
stdscr.keypad(False)

curses.endwin()

Complex

import curses

def main(stdscr):
  # Clear screen
  stdscr.clear()
  
  while True:
    # Store the key value in the variable {c}
    c = stdscr.getch()
    # Clear the terminal
    stdscr.clear()
    if c == ord('a'):
      stdscr.addstr("You pressed the 'a' key.")
    elif c == curses.KEY_UP:
      stdscr.addstr("You pressed the up arrow.")
    else:
      stdscr.addstr("This program doesn't know that key...")

curses.wrapper(main)

Finally ^{steven.codes YouTube}

import time, curses
def main(stdscr):
  # Make stdscr.getch non-blocking
  stdscr.nodelay(True)
  width = 4
  count = 0
  direction = 1
  while True:
    c = stdscr.getch()
# Clear out anything else the user has typed in
    curses.flushinp()
    stdscr.clear()
# If the user presses 'p', increase the width of the springy bar
    if c == ord('p'):
      width += 1
    # Draw a springy bar
    stdscr.addstr("#" * count)
    count += direction
    if count == width:
      direction = -1
    elif count == 0:
      direction = 1
# Wait 0.1 seconds
    time.sleep(0.1)
curses.wrapper(main)